LibHTML: Add Selector::specificity(), which returns a Specificity object.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/9a7dc065676

LibHTML/CSS/Selector.cpp

@@ -8,3 +8,28 @@ Selector::Selector(Vector<Component>&& components)
 Selector::~Selector()
 {
 }
+
+Specificity Selector::specificity() const
+{
+    unsigned ids = 0;
+    unsigned tag_names = 0;
+    unsigned classes = 0;
+
+    for (auto& component : m_components) {
+        switch (component.type) {
+        case Component::Type::Id:
+            ++ids;
+            break;
+        case Component::Type::Class:
+            ++classes;
+            break;
+        case Component::Type::TagName:
+            ++tag_names;
+            break;
+        default:
+            break;
+        }
+    }
+
+    return { ids, classes, tag_names };
+}

LibHTML/CSS/Selector.h

@@ -2,11 +2,17 @@
 
 #include <AK/AKString.h>
 #include <AK/Vector.h>
+#include <LibHTML/CSS/Specificity.h>
 
 class Selector {
 public:
     struct Component {
-        enum class Type { Invalid, TagName, Id, Class };
+        enum class Type {
+            Invalid,
+            TagName,
+            Id,
+            Class
+        };
         Type type { Type::Invalid };
         String value;
     };
@@ -16,6 +22,8 @@ public:
 
     const Vector<Component>& components() const { return m_components; }
 
+    Specificity specificity() const;
+
 private:
     Vector<Component> m_components;
 };

LibHTML/CSS/Specificity.h

@@ -0,0 +1,34 @@
+#pragma once
+
+class Specificity {
+public:
+    Specificity(unsigned ids, unsigned classes, unsigned tag_names)
+        : m_ids(ids)
+        , m_classes(classes)
+        , m_tag_names(tag_names)
+    {
+    }
+
+    unsigned ids() const { return m_ids; }
+    unsigned classes() const { return m_classes; }
+    unsigned tag_names() const { return m_tag_names; }
+
+    bool operator<(const Specificity& other) const
+    {
+        return m_ids < other.m_ids
+            || m_classes < other.m_classes
+            || m_tag_names < other.m_tag_names;
+    }
+
+    bool operator==(const Specificity& other) const
+    {
+        return m_ids == other.m_ids
+            || m_classes < other.m_classes
+            || m_tag_names < other.m_tag_names;
+    }
+
+private:
+    unsigned m_ids { 0 };
+    unsigned m_classes { 0 };
+    unsigned m_tag_names { 0 };
+};